Horns Inoperative. Chevrolet PJJ 2001

For 1990-2009 cars

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. Verifies that the body control module (BCM) is providing ground to the horn relay.

2. Tests for voltage at the battery positive voltage terminal of the horn relay coil.

3. Tests for voltage at the battery positive voltage terminal of the horn relay switch. The HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.

4. The horns need maximum current flow to operate properly. A high resistance (greater than 0.5ohms) in the horn control circuit or the horn ground circuit could cause operating problems with the horns. Inspect the circuits for faults that would restrict current flow.

5. The horn relay control circuit includes the horn slip ring and the horn switch. The horn slip ring and the horn switch must be tested for a high resistance, an open or a short to voltage when testing the relay control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Horns Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Horns
2 | Depress the horn switch. Does the horn operate? | -- | Go to Step 3 | Go to Step 5

3

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, command the Body Control Module Horn Output ON and OFF.

Does the horn operate?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4 | Test the body control module (BCM) portion of the horn relay control circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 13

5

1. Turn OFF the ignition.
2. Disconnect the horn relay.
3. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and a good ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 16

6

1. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit.
2. Depress and hold the horn switch.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 17

7 | Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 18
8 | Momentarily connect a 15 amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the horn control circuit. Does the horn operate? | -- | Go to Step 14 | Go to Step 9
9 | Reconnect the horn relay. Disconnect the horn connector. Connect a test lamp between the horn control circuit and a good ground. Depress and hold the horn switch. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 19
10 | Connect a test lamp between the horn control circuit and the horn ground circuit. Depress and hold the horn switch. Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 20
11 | Inspect for poor connections at the horn. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 12

12

1. Connect a 15 amp fused jumper wire between the positive battery terminal and the control terminal of the horn.
2. Connect another jumper wire between the negative battery terminal and the ground terminal of the horn.

Does the horn operate?

--

Go to Step 15

Go to Step 23

13 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 21
14 | Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 24 | Go to Step 22
15 | Repair the high resistance in the horn control circuit or the horn ground circuit. (A resistance as low as 0.5ohms could cause operating problems with the horns). Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 24 | --
16 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 24 | --
17 | Repair the open or short to voltage in the horn relay control circuit. (The horn relay control circuit includes the horn slip ring and the horn switch.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 24 | --
18 | Repair the open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 24 | --
19 | Repair the open or high resistance in the horn control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 24 | --
20 | Repair the open or high resistance in the horn ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 24 | --
21 | Important: Perform the BCM programming procedure when replacing the BCM. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the repair? | -- | Go to Step 24 | --
22 | Replace the horn relay. Did you complete the replacement? | -- | Go to Step 24 | --
23 | Replace the horn. Refer to Horn Replacement . Did you complete the replacement? | -- | Go to Step 24 | --
24 | Operate the horn. Does the horn operate properly? | -- | System OK | Go to Step 1